This invention relates to blades for cutting electronic crystals and substrates or the like and more particularly to such blades which are flexible and self-supporting.
Blades for cutting electronic crystals and substrates or the like are used extensively in the semiconductor industry. Such electronic crystals and substrates include germanium, gallium arsenide, silicon, quartz, aluminum oxide, beryllium oxide, sapphire, glass and others. Using silicon as an example, a silicon crystal is first sliced into wafers by a large slicing saw. A large number of semiconductor devices are then photofabricated onto each wafer. Cutting or dicing blades are then used to dice the wafer to separate the semiconductor devices, or chips, fabricated thereon.
Existing cutting blades, however, are not without disadvantages. Some dicing blades, for example, consist of a plating of nickel and diamond on an aluminum hub support, the volume of the nickel being greater than 80% of the volume of the plating. These blades are difficult and expensive to make. The nickel is plated in the shape of a narrow ring near the outer margin of the aluminum hub. Subsequently a peripheral portion of the hub is etched away to expose a narrow rim of the nickel-diamond cutting surface. The aluminum hub support for these blades must be machined to very small tolerances, usually 0.0001" (0.00025 cm). But the expense of this machining is wasted if the nickel-diamond plating on the hub is defective. Likewise the hub must be discarded if the cutting surface created by etching back the hub is too large, too small, or otherwise defective. The etching process is very inexact, resulting in a large parts-failure rate. On the other hand, if a satisfactory nickel-diamond cutting surface is formed on a hub, but the hub is for some reason defective, e.g., improperly machined, again the entire hub-cutting surface combination must be discarded. Thus, the cost of these blades is high. An additional disadvantage of these blades is that they are not reuseable: once the cutting portion of the blade has worn down, the blade must be thrown away. Finally, because the width of the hub and the diameter of the nickel-diamond cutting surfaces vary from blade to blade, the dicing saw must be realigned each time a new blade is put on the saw.
Other metal-diamond dicing blades are made by pressing diamond particles into a thin sheet of metal. The diamond particles, however, only enter the exterior of the metal sheet and therefore do not uniformly disperse throughout the metal sheet. As a result, the flat sides of these blades have a substantial concentration of diamond particles, but the cutting edge or rim of the blade has a much lower concentration.
Copper-diamond and bronze-diamond dicing blades are formed by sintering. These sintered blades, however, cannot be made thinner than about three mils, which generates a cut or kerf wider than desired. Such blades tend to warp during the sintering process, especially blades as thin as three mils, so thin sintered blades are an expensive, limited-production, special-order item.
Dicing blades are also made of diamond powder bonded in a phenolic resin. These phenolic blades wear faster and are more fragile than the diamond-nickel blades.
No matter what type of dicing blade is used, an overriding problem is getting the cutting surface of the blade perpendicular to the crystal or substrate being cut. Cutting at any angle other than 90.degree. results in a cut which is too wide, thereby wasting valuable material.
Prior art dicing wheels are described in "Dicing Wheels for Wafer Separation," Electronic Packaging & Production, July, 1977, Vol. 17, p. 196.